From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752730AbcGMKDF (ORCPT ); Wed, 13 Jul 2016 06:03:05 -0400 Received: from mail-oi0-f67.google.com ([209.85.218.67]:33886 "EHLO mail-oi0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750854AbcGMKC5 (ORCPT ); Wed, 13 Jul 2016 06:02:57 -0400 Subject: Re: [RFC PATCH 4/4] KVM: vmx: add support for emulating UMIP To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1468351223-3250-1-git-send-email-pbonzini@redhat.com> <1468351223-3250-5-git-send-email-pbonzini@redhat.com> <8f893604-1e80-2979-bc87-45a049238e58@gmail.com> <4e7bab78-61cf-271e-9fb9-685d217f8d0d@redhat.com> From: Yang Zhang Message-ID: Date: Wed, 13 Jul 2016 18:02:46 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <4e7bab78-61cf-271e-9fb9-685d217f8d0d@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/7/13 17:35, Paolo Bonzini wrote: > > > On 13/07/2016 11:21, Yang Zhang wrote: >>> >>> +static int handle_desc(struct kvm_vcpu *vcpu) >>> +{ >>> + WARN_ON(!(vcpu->arch.cr4 & X86_CR4_UMIP)); >> >> I think WARN_ON is too heavy since a malicious guest may trigger it always. > > I missed this---how so? Setting the bit is under "if ((cr4 & > X86_CR4_UMIP) && !boot_cpu_has(X86_FEATURE_UMIP))". Sorry, I consider it under my previous suggestion(setting it unconditionally). :( -- Yang Alibaba Cloud Computing